Butadiene inhalation accelerates arteriosclerotic plaque development in cockerels

Effect of vinyl chloride exposure on cardiometabolic toxicity

Vinyl chloride (VC) is an organochlorine mainly used to manufacture its polymer polyvinyl chloride, which is extensively used in the manufacturing of consumer products. Recent studies suggest that chronic low dose VC exposure affects glucose homeostasis in high fat diet-fed mice. Our data suggest that even in the absence of high fat diet, exposure to VC (0.8 ppm, 6 h/day, 5 day/week, for 12 weeks) induces glucose intolerance (1.0 g/kg, i.p.) in male C57BL/6 mice. This was accompanied with the depletion of hepatic glutathione and a modest increase in lung interstitial macrophages. VC exposure did not affect the levels of circulating immune cells, endothelial progenitor cells, platelet-immune cell aggregates, and cytokines and chemokines. The acute challenge of VC-exposed mice with LPS did not affect lung immune cell composition or plasma IL-6. To examine the effect of VC exposure on vascular inflammation and atherosclerosis, LDL receptor-KO mice on C57BL/6 background maintained on western diet were exposed to VC for 12 weeks (0.8 ppm, 6 h/day, 5 day/week). Unlike the WT C57BL/6 mice, VC exposure did not affect glucose tolerance in the LDL receptor-KO mice. Plasma cytokines, lesion area in the aortic valve, and markers of lesional inflammation in VC-exposed LDL receptor-KO mice were comparable with the air-exposed controls. Collectively, despite impaired glucose tolerance and modest pulmonary inflammation, chronic low dose VC exposure does not affect surrogate markers of cardiovascular injury, LPS-induced acute inflammation in C57BL/6 mice, and chronic inflammation and atherosclerosis in the LDL receptor-KO mice.

The association between urinary levels of 1,3-butadiene metabolites, cardiovascular risk factors, microparticles, and oxidative stress products in adolescents and young adults

1,3-Butadiene (BD) is a synthetic colorless gas used in the production of synthetic rubber and polymers. Exposure to BD has been reported to increase oxidative stress and accelerate atherosclerosis in vitro and in animal studies. In occupational studies, BD exposure has been linked to cardiovascular disease (CVD). However, no previous research has been reported on whether BD exposure is associated with CVD risk factors and oxidative stress in the general population. We recruited 853 young participants to study the correlation between urinary levels of the BD metabolite, N-acetyl-S-(3,4-dihydroxybutyl)-L-cysteine (DHBMA), CVD risk factors, serum levels of endothelial microparticles and platelet microparticles, and the urinary levels of 8-hydroxydeoxyguanosine (8-OHdG). The results showed the DHBMA levels were positively correlated with low-density lipoprotein-C, carotid intima-media thickness (CIMT), CD31+/CD42a - counts (endothelial apoptosis markers), and urinary 8-OHdG levels. Moreover, DHBMA levels were negatively correlated with CD62 P counts (platelet activation marker). The correlation between DHBMA, CIMT, and 8-OHdG was more evident when the levels of CD31+/CD42a - or CD62 P were above 50%. In conclusion, we reported that the urinary levels of DHBMA were associated with the lipid profile, CIMT, microparticles, and marker of oxidative stress in this young population. Future studies on BD exposure and atherosclerosis are needed.

Crotonaldehyde-induced vascular relaxation and toxicity: Role of endothelium and transient receptor potential ankyrin-1 (TRPA1)

INTRODUCTION

Crotonaldehyde (CR) is an electrophilic α,β-unsaturated aldehyde present in foods and beverages and is a minor metabolite of 1,3-butadiene. CR is a product of incomplete combustion, and is at high levels in smoke of cigarettes and structural fires. Exposure to CR has been linked to cardiopulmonary toxicity and cardiovascular disease.

OBJECTIVE

The purpose of this study was to examine the direct effects of CR in murine blood vessels (aorta and superior mesenteric artery, SMA) using an in vitro system.

METHODS AND RESULTS

CR induced concentration-dependent (1-300 μM) relaxations (75-80%) in phenylephrine (PE) precontracted aorta and SMA. Because the SMA was 20× more sensitive to CR than aorta (SMA EC50 3.8 ± 0.5 μM; aorta EC50 76.0 ± 2.0 μM), mechanisms of CR relaxation were studied in SMA. The CR-induced relaxation at low concentrations (1-30 μM) was inhibited by: 1) mechanically-impaired endothelium; 2) Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME); 3) guanylyl cyclase (GC) inhibitor (ODQ); 4) transient receptor potential ankyrin-1 (TRPA1) antagonist (A967079); and, 5) by non-vasoactive level of nicotine (1 μM). Similarly, a TRPA1 agonist, allyl isothiocyanate (AITC; mustard oil), stimulated SMA relaxation dependent on TRPA1, endothelium, NO, and GC. Consistent with these mechanisms, TRPA1 was present in the SMA endothelium. CR, at higher concentrations (100-300 μM), induced tension oscillations (spasms) and irreversibly impaired contractility (a vasotoxic effect enhanced by impaired endothelium).

CONCLUSIONS

CR relaxation depends on a functional endothelium and TRPA1, whereas vasotoxicity is enhanced by endothelium dysfunction. Thus, CR is both vasoactive and vasotoxic along a concentration continuum.

Glutathione S-Transferase T1 (GSTT1) Null Polymorphism, Smoking, and Their Interaction in Coronary Heart Disease: A Comprehensive Meta-Analysis

BACKGROUND

The association between glutathione S-transferase T1 (GSTT1) null polymorphism and coronary heart disease (CHD) is inconsistent among studies, and data on the GSTT1 null genotype-smoking interplay in CHD is lacking. We conducted this meta-analysis to investigate the relationship between GSTT1 null polymorphism and CHD and to assess the potential interaction between GSTT1 null genotype and smoking.

METHODS

PubMed and EMBASE databases were searched up to 27 January 2016 using the appropriate terms. Odds ratios were pooled using either fixed-effects or random-effects models.

RESULTS

Twenty-nine articles including 31 studies with 15,004 cases and 35,597 controls were eligible. The random-effects model showed that the GSTT1 null genotype was associated with increased CHD risk (OR=1.213, 95%CI: 1.004-1.467; I²=90.4%). After excluding 10 studies detected by Galbraith plot, the fixed effects summary estimate also showed an increased risk of CHD (OR=1.14, 95% CI: 1.06-1.22; I²=27.7%). A case-only analysis including eight studies showed a statistically significant positive interaction between GSTT1 null polymorphism and smoking status on CHD (OR=1.34, 95% CI: 1.09-1.64; I²=0%). Sensitivity analyses further supported the associations. No publication bias was observed.

CONCLUSIONS

This meta-analysis suggests that GSTT1 null polymorphism is associated with the risk of CHD. To our knowledge, this is the first meta-analysis to prove a positive effect of the interaction between GSTT1 null genotype and smoking status on the risk of CHD. Future studies with detailed individual information are needed to confirm our findings.

Glutathione S-transferase gene polymorphism as a susceptibility factor for acute myocardial infarction and smoking in the North Indian population

OBJECTIVES

Glutathione S-transferase (GST) plays a key role in the detoxification of xenobiotic atherogens generated by smoking. We investigated whether functional GST gene polymorphism might be associated with acute myocardial infarction (AMI) and smoking. No such investigation has previously been conducted among North Indians.

METHODS

230 patients with AMI and 300 healthy controls of North Indian ethnicity were enrolled in the study. GSTM1/T1/P1 gene polymorphisms were examined using restriction fragment length polymorphism.

RESULTS

When GST polymorphism was analyzed in patients with AMI, GSTM1 null genotype frequencies were 0.24 and 0.21 among cases with coronary artery disease and controls, respectively. The respective GSTT1 null genotype frequencies were 0.10 and 0.20 (p = 0.001). GSTP1 variant Val/Val allele frequencies were 0.02 and 0.07 with p = 0.03. After risk factor adjustment, only GSTP1Val/Val was found to be protective against disease. Considering the effect of GST (T1, M1, and P1) gene polymorphism on smoking, subjects were further divided into smokers and nonsmokers. However, GSTT1 null as well as GSTP Val/Val genotypes were protective only in nonsmokers (p = 0.01 and p = 0.04).

CONCLUSIONS

A significant protective effect of GSTT1 null and GSTP1 Val genotype against disease was observed in patients with AMI although protection was limited to nonsmokers.

Could charcoal filtration of cigarette smoke reduce smoking-induced disease? A review of the literature

A review of the published work with charcoal-filtered cigarettes indicates that there are reductions in the concentrations for many gas-vapor phase constituents found in mainstream smoke. However, charcoal filters provided no apparent capacity for reduction of smoke particulate phase components. The reductions in gas-vapor phase smoke chemistry analytes generally correspond with findings of reduced toxicological activity, principally related to a reduction in the cytotoxic action of the volatile smoke constituents. Results of a short-term clinical study show small reductions in the biomarkers of the gas-vapor phase smoke constituents in subjects smoking charcoal-filtered cigarettes, compared to subjects smoking non-charcoal filtered cigarettes. The very limited epidemiology data (a single study) fail to demonstrate a conclusive beneficial effect of charcoal-filtered cigarette products compared to non-charcoal filtered cigarette products. Review of the scientific literature is hindered due to the lack of documentation regarding the activity of the charcoal used in the filter, and the inconsistency in product designs used between the various different disciplines (chemistry, pre-clinical, clinical and epidemiology) that have conducted studies with charcoal filtered cigarettes. There do not appear to be any published studies using a combination of data from the different disciplines based on a consistently designed charcoal cigarette filter. Although the literature presently available would suggest that smoke filtration provided by current charcoal filter techniques alone may not be substantial enough to reduce smoking-related disease, the data are limited. Therefore, for the reduction of smoking-induced disease, it is difficult to come to a definitive conclusion regarding the potential health benefits of using charcoal as a smoke filtration technology.

T null and M null genotypes of the glutathione S-transferase gene are risk factor for CAD independent of smoking

Background

The association of the deletion in GSTT1 and GSTM1 genes with coronary artery disease (CAD) among smokers is controversial. In addition, no such investigation has previously been conducted among Arabs.

Methods

We genotyped 1054 CAD patients and 762 controls for GSTT1 and GSTM1 deletion by multiplex polymerase chain reaction. Both CAD and controls were Saudi Arabs.

Results

In the control group (n = 762), 82.3% had the T ^wild M ^wildgenotype, 9% had the T^wild M ^null, 2.4% had the T^null M ^wild and 6.3% had the T^null M ^null genotype. Among the CAD group (n = 1054), 29.5% had the T^wild M ^wild genotype, 26.6% (p < .001) had the T^wild M ^null, 8.3% (p < .001) had the T^null M ^wild and 35.6% (p < .001) had the T^null M ^null genotype, indicating a significant association of the T^wild M ^null, T^null M ^wild and T^null M ^null genotypes with CAD. Univariate analysis also showed that smoking, age, hypercholesterolemia and hypertriglyceridemia, diabetes mellitus, family history of CAD, hypertension and obesity are all associated with CAD, whereas gender and myocardial infarction are not. Binary logistic regression for smoking and genotypes indicated that only M ^null and T^nullare interacting with smoking. However, further subgroup analysis stratifying the data by smoking status suggested that genotype-smoking interactions have no effect on the development of CAD.

Conclusion

GSTT1 and GSTM1 null-genotypes are risk factor for CAD independent of genotype-smoking interaction.

Cardiovascular implications of exposure to traffic air pollution during exercise

Regular aerobic exercise is recommended by physicians to improve health and longevity. However, individuals exercising in urban regions are often in contact with air pollution, which includes particles and gases associated with respiratory disease and cancer. We describe the recent evidence on the cardiovascular effects of air pollution, and the implications of exercising in polluted environments, with a view to informing clinicians and other health professionals. There is now strong evidence that fine and ultra fine particulate matter present in air pollution increases cardiovascular morbidity and mortality. The main mechanisms of disease appear to be related to an increase in the pathogenic processes associated with atherosclerosis. People exercising in environments pervaded by air contaminants are probably at increased risk, due to an exercise-induced amplification in respiratory uptake, lung deposition and toxicity of inhaled pollutants. We make evidence-based recommendations for minimizing exposure to air-borne toxins while exercising, and suggest that this advice be passed on to patients where appropriate.

Toxicological evaluation of an electrically heated cigarette. Part 1: Overview of technical concepts and summary of findings

This series of papers provides a description of the toxicological evaluation of an electrically heated cigarette (EHC). With this novel cigarette design the tobacco is heated by a series of electric heating elements, which allows for greater control of the available heat and results in lower temperatures and less combustion compared with conventional lit-end cigarettes. This design was subjected to testing, including an evaluation of smoke chemistry, in vitro bacterial genotoxicity, in vitro mammalian cell cytotoxicity and a 90-day smoke inhalation study in rats. A conventional lit-end cigarette, the University of Kentucky Reference Cigarette 1R4F, was used as a point of comparison in these experiments. When adjusted for the yield of total particulate matter, the EHC delivered 50% lower amounts of about two-thirds of the 69 smoke constituents measured. Mutagenic activity (Salmonella reverse mutation assay) of the particulate phase material in the presence of metabolic activation was ca. 90% lower, with a slight reduction of activity in the absence of metabolic activation. Cytotoxic activity (neutral red assay) of the particulate phase material was ca. 40% lower, with about equal activity of the gas/vapor-phase material. Equal activity was noted between cigarette types in a whole smoke rat inhalation assay. The results from this series of tests demonstrate that the EHC produces a much different smoke--with an at least partially reduced yield of smoke constituents and biological activity--from that of a standard reference cigarette.

Nicotine does not influence arterial lipid deposits in rabbits exposed to second-hand smoke

BACKGROUND

Second-hand smoke (SHS) accelerates atherogenesis and impairs vascular function. The role of nicotine in this process has not been defined.

METHODS AND RESULTS

To examine the potential effects of nicotine on atherogenesis and vascular function, 48 rabbits receiving a 0.5% cholesterol diet were randomized to control (cholesterol diet only), SHS from nicotine-standard research cigarettes (SHS-ST), and SHS from nicotine-free research cigarettes (SHS-NF). The SHS rabbits were exposed to 48 nicotine-standard (12 animals) or nicotine-free (12 animals) cigarettes/d, 5 d/wk for 10 weeks. Air carbon monoxide and particulates and plasma carboxyhemoglobin were significantly higher in the 2 SHS groups than the control group (P<0.001). The SHS-ST group had significant increases in plasma nicotine and cotinine compared with the other groups (P<0.001). There was no difference in serum lipids. Lipid lesions were increased in both SHS groups (54+/-5% [SEM] aorta and 66+/-4% pulmonary artery, 53+/-7% and 69+/-4%, and 39+/-4% and 43+/-3% in the SHS-ST, SHS-NF, and control groups, respectively; P=0.049 aorta and P<0.001 pulmonary artery).

CONCLUSIONS

SHS exposure increased arterial lipid lesions, but nicotine did not contribute significantly to this effect. This effect is presumably due to other combustion products in the smoke.